Video compression systems are employed to reduce the number of bits needed to transmit and store a digital video signal. As a result, a lower bandwidth communication channel can be employed to transmit a compressed video signal in comparison to an uncompressed video signal. Similarly, a reduced capacity of a storage device, which can comprise a memory or a magnetic storage medium, is required for storing the compressed video signal. A general video compression system includes an encoder, which converts the video signal into a compressed signal, and a decoder, which reconstructs the video signal based upon the compressed signal.
In the design of a video compression system, an objective is to reduce the number of bits needed to represent the digital video signal while preserving its visual content. Current methods and systems for video compression have achieved a reasonable quality of content preservation at a transmission bit rate of 56 kilobits per second. These methods and systems are based upon directly compressing a waveform representation of the digital video signal.
Motion compensation is one approach which is utilized in many video compression schemes. Current approaches model motion in terms of simple displacements of blocks or a global transformation of an entire scene from a reference video frame. A disadvantage of this approach is that reference video frames have to be continuously updated and hence the video compression system must always compress an appreciable number of bits. This is inefficient when the displacements or transformations can be predicted.